The present invention relates to improvements in torsional vibration dampers, and more particularly to improvements in apparatus which embody one or more dampers to prevent the transmission of torsional vibrations and/or other stray movements from a rotary input component to a rotary output component which can rotate with and relative to the input component.
It is already known to prevent the transmission of undesirable vibratory and/or other stray movements from a rotary input component to a rotary output component by resorting to torque transmitting means in the form of several torsional vibration dampers. For example, the torque transmitting means can comprise a first or auxiliary damper with coaxial rotary input and output elements and one or more energy storing devices (such as coil springs) between such elements, and a second or main damper with energy storing devices which are normally stiffer (i.e., more resistant to deformation) than the energy storing device or devices of the first damper.
Apparatus with plural torsional vibration dampers are disclosed, for example, in published German patent applications Serial Nos. 41 41 643 and 40 31 762. Each such apparatus can be utilized in the power train of a motor vehicle (e.g., as a clutch disc or clutch plate in a manually operable or automated friction clutch) and comprises a first (so-called idling) torsional vibration damper or system as well as a second or main or primary damper or load system. The first damper is equipped with abutments or stops which prevent further deformation of its energy storing device or devices when the torque being transmitted by the first damper rises to a preselected value; if the input and output components of such torsional vibration damping apparatus continue to turn relative to each other, the torsional vibration damping operation is taken over by the main damper. That torque at which the first damper becomes ineffective and the damping operation is taken over by the main damper is any torque that exceeds the so-called idling torque; for example, idling torque is that torque which is being transmitted by the clutch disc or clutch plate of a fully engaged friction clutch when the engine is running to drive a flywheel of the clutch but the transmission (which receives torque from the clutch disc) is shifted into neutral gear. At such time, the engine-driven flywheel cooperates with an axially movable rotary pressure plate of the friction clutch to drive the clutch disc (e.g., with minimal slip or without slip between the friction surfaces of the flywheel and the clutch disc on the one hand, and the respective sets of friction linings of the clutch disc on the other hand) but the clutch disc cannot cause the wheels of the motor vehicle to rotate because the transmission which is to transmit torque from the clutch disc to the wheels is disengaged, i.e., in neutral gear. The just described mode of assembling and operating the power train of a motor vehicle has been found to be highly satisfactory under a wide variety of circumstances of operation or use of a motor vehicle wherein a friction clutch with a clutch disc is designed to transmit torque from a prime mover (such as a combustion engine) to the driven wheels by way of an automated or manually shiftable transmission and (if necessary) a differential for the live axles.
Published German patent application Serial No. 195 22 225 and the corresponding U.S. patent application Ser. No. 08/475,295 disclose modified torsional vibration damping apparatus with two dampers which operate in series. The construction and the mode of operation of the first damper in such apparatus constitute improvements over and further developments of the construction and mode of operation of first dampers which are disclosed in the aforementioned published German patent applications Serial Nos. 41 41 643 and 40 31 762.
The disclosures of all U.S. patents and allowed U.S. patent applications, as well as of all U.S. patents and/or allowed U.S. patent applications corresponding to foreign patents and/or patent applications, enumerated in this specification are to be considered as being incorporated herein by reference.